The present invention relates to protective power controllers for operating electrical and electronic circuitry and, more particularly, to protective power controllers for multiple loads.
Supplying electrical power to loads has long been recognized as requiring some protective means associated therewith to protect the power supply arrangement in case of malfunctions in the load leading to unexpectedly large power dissipation therein. A number of different kinds of protective means have been used including fuses, circuit breakers or other circuit arrangements which disrupt the supply of power to the load because of same malfunction therein.
Electronic power controllers with protective means provided therein are attractive for use with loads which are to be supplied power under the control of other devices such as computers. Such electronic power controllers can be operated through input signals provided thereto to control the supplying of power to the load or loads and the cessation of same very conveniently.
Further, electronic power controllers can very rapidly detect conditions indicating a malfunction in a load, and so very quickly shut off further supply of power to that malfunctioning load. Better yet, electronic power controllers can be configured to periodically review the situation at the load to determine if the malfunction condition has ended and, if so, to then again permit power to be applied to that load. Thus, if the duration of the period between such reviews is sufficiently short, little time need be lost between the disappearance of a malfunction condition and the resupply of power to the load.
The period of such load malfunction reviews in an electronic power controller is typically set by a timer which keeps power from the load for the duration of the selected timer timing period. Thereafter, power is again supplied to the load and sensing determines whether the malfunction continues to exist. If so, the timer is again initiated and power is removed from the load until the end of the succeeding timer timing period. This cyclic reviewing continues until the malfunction ends, after which power can again be continuously supplied to the load.
This mode of operation provides some difficulties if an electronic power controller is used with several outputs to operate several loads. Use of such a timer to control the circuits for each output leads to having the timer, if initiated by one malfunctioning load, terminate the supply of power to all of these loads from the corresponding output circuits, even those output circuits which do not have malfunctioning loads connected to them. On the other hand, the use of an individual timer circuit for each output control circuit adds considerably to the amount of circuitry which must be provided in the multiple output electronic power controller. Yet, at the same time in this situation, the use of a temperature sensing means to sense the temperature reached by the electronic power controller structure in supplying power to the multiple loads usually demands that the sensing means be able to terminate the supply of power from all of the output circuits in the controller. Also, once such output circuits are directed to cease the supply of electrical power to the power controller outputs, such outputs should be prevented from supplying current to the loads connected thereto no matter where the other sides of those loads are additionally connected, which can vary if the controller is to be able to both selectively provide current to and from such loads. Thus, there is desired an electronic power controller having multiple outputs having the capabilities needed to avoid the difficulties just mentioned.